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-   -   We can not hear group-delay under 100Hz? (http://www.diyaudio.com/forums/multi-way/226585-we-can-not-hear-group-delay-under-100hz.html)

Helmuth 28th December 2012 05:56 PM

We can not hear group-delay under 100Hz?
 
Hi, I want to open a discussion if group-delay is audible under 100Hz.

I doubt it is audible because we can not locate a subwoofer under approximately 200Hz.

As an example if bass travels 6 meter we also have a delay of 18 msec. And we would be able to locate the subwoofer when we could hear that.

Because the group-delay is the result of a resonant system the delay increases when it becomes more resonant. I think when there is poor damping of this resonance the group-delay is audible. Not that we can qualify the delay time it self.


Groupdelay of a closed box and a bass-reflex that is more resonant.
http://i220.photobucket.com/albums/d...psa2a9b834.png

There is a rule of the thum that the delaytime in msec X frequency = <400 the delay isn't audible.

So what is your opinion about that?

sreten 28th December 2012 06:40 PM

Hi,

Group delay is an inevitable consequence of a speakers bass roll-off,
and asking if its audible makes no sense, as of course a speakers
bass roll-off is clearly audible in your room, and modified by your
room, which will effect the real acoustic group delay.

A very misunderstood parameter, that cannot be separated from
the actual response, but can be used to talk about the response.

Maximally flat vented responses are poor IMO in real rooms, in terms
of group delay I could say the peaking of group delay is bad but
that is really only obfuscating the real issues. BTW peaking is bad.

rgds, sreten.

You can hear peaks of group delay below 100Hz.

Soundtrackmixer 28th December 2012 07:06 PM

Quote:

Originally Posted by Helmuth (Post 3302211)
Hi, I want to open a discussion if group-delay is audible under 100Hz.

I doubt it is audible because we can not locate a subwoofer under approximately 200Hz.

That should be under 80hz. According to test done by THX, as you go above 80hz, it becomes easier and easier to locate the sub. Hence why they chose 80hz as their standard crossover point for THX components.

speakerdoctor 28th December 2012 09:03 PM

So, what does group delay sound like at whatever frequency it's audible? I'd like to know so I can listen for it.

Helmuth 28th December 2012 09:08 PM

A wise senior Dutch audiophile mentioned low frequent group-delay as you can heart some thing is wrong with the sound, without you can grab it whats wrong.

As I mentioned when a bas reflex tuning with high groupdelay has more resonant behavior, i think you can hear that.

SY 28th December 2012 09:10 PM

We did a double blind test here a year or so ago with an allpass filter in the midrange- for me, it made the image of an acoustic guitar seem slightly disjointed (for lack of a better word). You can easily find out for yourself- using a music editing program like Goldwave, you can put in whatever group delay you like at whatever frequencies you like without changing the frequency response, then compare before and after.

Calvin 29th December 2012 09:27 AM

Hi,

at first glance the group delay seems like a measure of how precise and tight low bass may sound. We tested and measured different solutions in a anechoic chamber. Starting from Dipoles with <6ms over CB ~6-10ms going to >>10ms with BR and BPs, presicision becomes lower and the well known boominess comes into play. Now the amplitude responses still differed. A Bassboost for Dipole and CB , equalized to similar amplitude response as BR would introduce group delay of similar dimension. Still though the equalized Dipole as well as the CB sounded cleaner and more natural than BR and BP. This finding would disclude the group delay as the deciding parameter, if there weren´t a difference in ´electrical´ group delay and ´mechanical´ group delay. I haven´t heard of or seen a paper discussing any possible audible differences between electrical and mechanical group delay.
So I´d rather dismiss GD as parameter.

jauu
Calvin

Helmuth 29th December 2012 09:49 AM

It sounds like a contradiction your reply.

There is a poorer response of BR and BP with higher GD.

And you want as end conclusion dismiss GD as parameter?


Or you are saying resonant systems like BR and BP give poor results not due GD.

sreten 29th December 2012 12:20 PM

Quote:

Originally Posted by speakerdoctor (Post 3302379)
So, what does group delay sound like at whatever frequency it's audible?
I'd like to know so I can listen for it.

Hi,

Group delay is not an independent parameter you can adjust,
its a consequence of the bass alignment you use and just
one of the ways of describing the alignments properties.

It easy to hear different bass alignments, thus different GD.

What is not easy is discussing GD correctly in context.

rgds, sreten.

jerome69 29th December 2012 01:20 PM

Helmuth, have you seen this ? : Discussion of Group Delay in Loudspeakers

I think GD greater than 10ms below 100Hz is audible.


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